1. Technical Field
The present invention is generally directed to a processing system that executes a fast boot wake-up. More particularly, the present invention may execute the fast boot wake-up operation through selective copying of an image filesystem during system boot.
2. Related Art
Processing systems, such as embedded systems, are widely used in both consumer and commercial applications. Many applications, such as those involved in automotive telematics systems, impose significant constraints on the operation of the processing system. Constraints imposed on system power consumption may require that the system operate in a low-power mode. System response time constraints may require minimization of the system startup time and/or wake-up time.
It is often difficult to design a processing system that adequately balances power constraints and response time constraints with one another. Each time that the system enters a low-power mode (as dictated by the power constraints), it must execute a wake-up operation before it is ready to respond to various system events. The duration of the wake-up operation, however, should fall within the bounds of the response time constraints imposed on the system.
If the processor has been powered off during the low-power mode, the wake-up operation includes a complete reboot of the processing system. A complete reboot can be quite time consuming, particularly in embedded systems that employ an image filesystem. In such embedded systems, a complete copy of the image filesystem is transferred from read only memory to random access memory, where it is used by the processor. The image filesystem may contain the operating system for the embedded system, the executable programs used in the embedded system, and/or any data files that might be related to the programs. Consequently, it may be quite large and require a substantial amount of time and processing power to execute the transfer. During the transfer, the processing system is typically not responsive to most of the events that the system is designed to handle. The response time of the system is therefore impacted by the duration of the transfer.
Attempts have been made to design a processing system having a low-power mode from which a fast system recovery can be made. Most such attempts have involved driving the processor into a hibernation mode. However, even in the hibernation mode, the processor may place a substantial drain on the system power supply, thereby exceeding the power consumption constraints. Further, a significant amount of programming code may be required to properly implement this type of system. An improved system in which both a fast boot wake-up and a low-power mode are realized is therefore desirable. Further, an improved system in which a fast boot wake-up in response to other system events is desirable.